Frequently, there is a need or desire to sample and analyze a fluid stream contained in a conduit. One such example may involve vehicle exhaust systems wherein an engine's combustion air outflow is conveyed through the exhaust system. A sensor or sensors may be employed in the exhaust system to monitor the level of NOx, which is a generic term for the oxides of nitrogen. NOx may be produced during combustion from a reaction of the natural nitrogen and oxygen that exists in atmospheric air.